Our main interest centers around the mechanisms of DNA replication and recombination, their interrelation and the interaction of participating components. We are studying these mechanisms in phage T4 because this model system is excellently suited for combinations of genetic and biochemical studies. We would like to use the knowledge gained from such experiments to study the transfer of genetic information by DNA in eukaryotes. At first, we are using plants because they have the capacity to be regenerated from haploid protoplasts cells. In phage T4 we are particularly interested in the following questions: 1) Is T4 DNA replication initiated at one or several origins and what determines which origin(s) is/are used? 2) Are there several mechanisms of initiation of DNA replication? 3) To what extent is recombination involved or required in initiation of DNA replication? 4) How do certain enzymes recognize each other in different steps of recombination and replication; particularly, what is the role of the T4-DNA-binding protein in such recognition? 5) To what extent do phage and host functions substitute for or interfere with each other in DNA replication and recombination? These questions will be answered by using phage and host mutations which cause arrest of DNA replication and/or recombination at different intermediate steps and of secondary suppressor mutations. We will characterize by physical and genetic methods intracellular DNA produced by such mutants under restrictive conditions and viable progeny produced under semipermissive conditions. Our recent studies have shown that in vivo, recombination enzymes must act as complexes. We shall try to isolate such recombination complexes with the aim to determine the stochiometry of different proteins and with the hope to test functions of these proteins in vitro. Finally, we want to continue our studies on the uptake of homologous DNA by protoplasts of certain species of Solanaceae, in which flowering plants can be generated from a single haploid protoplast cell. This is being done in collaboration with investigators at the MP Institute for plant breeding research in Koln-Vogelsang.